Detection of main-effect and epistatic QTL for yield-related traits in rice under drought stress and normal conditions

Drought-resistant cultivars play an important role in maintaining high and stable crop yields under drought-stress conditions. However, the genetic mechanism of drought resistance must first be elucidated. Therefore, 220 recombinant inbred lines from a cross between Xiaobaijingzi (upland rice) and Kongyu 131 (Oryza sativa L.) were used to identify quantitative trait loci (QTLs) for yield and yield-component traits under drought stress and control conditions in Heilongjiang and Tieli. As a result, 23 main-effect QTLs and 11 digenic interactions were detected for four traits under the above two conditions. Of the main-effect QTLs, 10 and 8 were detected under control and drought-stress conditions, respectively; and five common QTLs were observed. In addition, five QTLs were found to be responsible for the difference across the two conditions. Among all epistatic QTLs, three types of epistatic QTLs were observed: one was between two main-effect QTLs, such as qPH-3-1 and qPH-7-2; one was between one locus with and another without main-effect, e. g., qPN-4 and qPN-3-2; and one was between two loci without main-effect, e.g., qYP-6-1 and qYP-12-2. In the above epistatic examples, their recombinant genotypes tended to reduce plant height and the number of grains per panicle and increase yield, respectively. Our results provide a good foundation for designed molecular breeding of drought-resistant rice.